They are not solid state drive.
New internal Western-Digital and Seagate Hard Disk Drive
Form Factor: 3.5 inch
7200 RPM
Interface: SATA 6.0Gb/s
Capacity: 500 GB
500 GB x 3 available, $10 each. (minimum buy 2)
Form Factor: 2.5 inch drive:
Interface: SATA
Capacity: 160GB
160 GB x 14 available, 4 for $20. (minimum buy 4)
Capacity: 250GB
250 GB x 17 available, 3 for $22. (minimum buy 3)
Capacity: 320GB
320 GB x 3 available, 3 for $24. (minimum buy 3)
Capacity: 500GB
500 GB x 34 available, $10 each. (minimum buy 2)